A conventional drill chuck typically comprises a chuck body, a plurality of jaws, a nut, and sleeves including a front sleeve and a rear sleeve. In the case of manual drill chucks additional bearing and bearing spacer are provided to reduce frictions.
In the structure of the conventional drill chuck, the rear sleeve and the bearing spacer are fixed onto the chuck body respectively. The jaws, usually three, are respectively inserted into three angled bores uniformly distributed around the chuck body of the drill chuck. The nut is fitted in a nut groove of the chuck body. The threads of the nut and the threads of the jaws together form a thread driving mechanism to drive the jaws into gripping relationship or loosening relationship.
In addition, a nut jacket may be disposed at the outside of the nut and fixedly connected to the nut. The front sleeve is mounted around the nut jacket and connected to the nut jacket through keys formed on the inner circumference wall of the front sleeve, key slots corresponding to the keys of the front sleeve are formed on the nut jacket. A block cover fixed to the front portion of the chuck body is provided to prevent the front sleeve from undesirable moving.
When the front sleeve is turned by hand, the front sleeve carries the nut jacket to turn accordingly, therefore the nut turns along with the nut jacket, which causes the jaws to move inwards or outwards along the angled bores in the chuck body due to the threads thereon, so the three jaws become fastened or released, therefore the handle of the drill tool is fastened by the jaws or released therefrom.
However, the conventional drill chuck with the above-described structures has a tendency to become loosening due to vibration or impact while using, which results in low reliability and bad security of the drill chuck.